A. Field of the Invention
This invention relates generally to a method for detecting leaks in pressurized piping systems and, in particular, to a method for detecting very small leaks of hydrocarbons, or like materials, in underground pressurized piping systems.
B. Background of the Invention
In gasoline service stations, it is common practice for automotive fuels to be stored in large underground tanks and pumped through underground product lines to various dispensing systems. In recent years, many steps have been taken to monitor and detect leakage from underground storage tanks and the associated product lines carrying the product to the dispensing systems. In that regard, the industry is continuously searching for new methods and technologies to enhance the ability to detect underground leakage from such systems in order to comply with regulations set by the Environmental Protection Agency (EPA), and other regulatory authorities.
In the past, serious problems have been created by leaks in underground piping, especially small but significant leaks of combustible explosive fluids which might go undetected for long periods of time. These problems are particularly critical in service stations, since the leakage of gasoline creates a serious hazard to life and property. Financial loss due to the escaping fluids is also a major problem. For these and other reasons, there has been a need within the industry for a simple, economical, and dependable system for detecting even minor leaks from underground product lines.
There have been several attempts in the prior art to provide a reliable, accurate, and economical method for detecting leaks from underground product lines based upon changes in flow rates, and/or measuring pressure within the product line. However, unlike the present inventive method, none of the prior art methods or techniques provided an economical system for detecting minor leaks while the product line was maintained at an elevated pressure due to continuous operation of the product pump. In addition, many of the prior systems are incapable of determining whether a product line is "tight", i.e., that the line does not have a leakage rate in excess of the minimum acceptable values set by various regulatory agencies.